Pin sqlalchemy to versions before 1.4

[uSpike]

If I try to run tests on master:

_____________________________________________________________________________________ ERROR collecting tests/test_database.py _____________________________________________________________________________________
ImportError while importing test module '/home/jordan/src/starlette/tests/test_database.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../.pyenv/versions/3.7.5/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_database.py:31: in <module>
    database = databases.Database(DATABASE_URL, force_rollback=True)
venv/lib/python3.7/site-packages/databases/core.py:66: in __init__
    backend_cls = import_from_string(backend_str)
venv/lib/python3.7/site-packages/databases/importer.py:21: in import_from_string
    raise exc from None
venv/lib/python3.7/site-packages/databases/importer.py:18: in import_from_string
    module = importlib.import_module(module_str)
../../.pyenv/versions/3.7.5/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
venv/lib/python3.7/site-packages/databases/backends/sqlite.py:8: in <module>
    from sqlalchemy.engine.result import ResultMetaData, RowProxy
E   ImportError: cannot import name 'RowProxy' from 'sqlalchemy.engine.result' (/home/jordan/src/starlette/venv/lib/python3.7/site-packages/sqlalchemy/engine/result.py)

It seems that sqlalchemy 1.4 changed the name from RowProxy to Row, and databases probably needs to be updated. This PR pins sqlalchemy to versions before 1.4 which is the quickest fix for the issue.

[tomchristie]

In favour of this, yup. Although this ought to be a fix against the databases package, rather than this one.

[tomchristie]

The databases setup.py there should be something like sqlalchemy==1.3.*

[uSpike]

There's also encode/databases#299 open to use sqlalchemy 1.4

[Kludex]

Does it still fail on 1.4.3? I didn't check the exact changes they made, but this is in the changelog:

• https://docs.sqlalchemy.org/en/14/changelog/changelog_14.html#change-1.4.3-engine

[uSpike]

@Kludex yes, my tests were run with 1.4.3

[tomchristie]

Latest databases release should now pin SQLAlchemy correctly.